A titanium alloy turbine wheel of the kind indicated above has the reputation of being difficult to access on the inside, given the plurality of adjacent annular cavities defined therein between the welded-together disks that constitute the wheel. The heat treatment required for preparing the part has the consequence of causing a contaminated layer to appear on the surface thereof (outside as well as inside), which layer is a few tens of micrometers thick, is rich in oxygen, and is known as the “alpha-case layer”. At present, only the outside of the part is pickled, since pickling the inside has previously been considered as being risky.
Unfortunately, the presence of this contaminated layer lies behind the formation of cracks that considerably shorten the lifetime of the part.